<template>
  <el-select
    :filterable="isFilterable"
    :value="valueTitle"
    :clearable="iscCearable"
    :filter-method="filterMethod"
    @clear="clearHandle"
    @change="$emit('change')"
    @visible-change="$emit('visible-change')"
    @remove-tag="$emit('remove-tag')"
    @blur="$emit('blur')"
    @focus="$emit('focus')"
  >
    <el-option :value="valueTitle" :label="valueTitle" class="select-tree-options">
      <el-tree
        id="tree-option"
        ref="selectTree"
        :accordion="accordion"
        :data="options"
        :props="props"
        :lazy="isLazy"
        :load="loadNode"
        :node-key="props.value"
        :default-expanded-keys="defaultExpandedKey"
        @node-click="handleNodeClick"
      ></el-tree>
    </el-option>
  </el-select>
</template>

<script>
export default {
  name: 'el-tree-select',
  props: {
    // 配置项
    props: {
      type: Object,
      default () {
        return {
          value: 'id', // ID字段名
          label: 'title', // 显示名称
          children: 'children' // 子级字段名
        }
      }
    },
    // 选项列表数据(树形结构的对象数组)
    options: {
      type: Array,
      default () {
        return {}
      }
    },
    // 初始值
    initialId: { type: String, default: null },
    // 可清空选项
    iscCearable: { type: Boolean, default: true },
    // 自动收起
    accordion: { type: Boolean, default: false },
    // 是否开启懒加载
    isLazy: { type: Boolean, default: false },
    // 是否开启搜索
    isFilterable: { type: Boolean, default: false }
  },
  data () {
    return {
      valueId: null,
      valueTitle: '',
      // 默认展开的数组
      defaultExpandedKey: []
    }
  },
  mounted () {
    this.valueId = this.initialId // 父组件传递给我初始ID
    // 初始化值
    this.initHandle()
  },
  methods: {
    // 初始化值
    initHandle () {
      if (this.valueId) {
        this.valueTitle = this.$refs.selectTree.getNode(this.valueId).data[this.props.label] // 初始化显示
        this.$refs.selectTree.setCurrentKey(this.valueId) // 设置默认选中
        this.defaultExpandedKey = [this.valueId] // 设置默认展开
      }
      this.initScroll()
    },

    // 初始化滚动条
    initScroll () {
      this.$nextTick(() => {
        const scrollWrap = document.querySelectorAll('.el-scrollbar .el-select-dropdown__wrap')[0]
        const scrollBar = document.querySelectorAll('.el-scrollbar .el-scrollbar__bar')
        scrollWrap.style.cssText = 'margin: 0px; max-height: none; overflow: hidden;'
        scrollBar.forEach(ele => (ele.style.width = 0))
      })
    },

    // 切换选项
    handleNodeClick (node) {
      this.valueTitle = node[this.props.label]
      this.valueId = node[this.props.value]
      this.$emit('getValue', this.valueId)
      this.defaultExpandedKey = []
    },

    // 清除选中
    clearHandle () {
      this.valueTitle = ''
      this.valueId = null
      this.defaultExpandedKey = []
      this.clearSelected()
      this.$emit('getValue', null)
    },

    // 清空选中样式
    clearSelected () {
      const allNode = document.querySelectorAll('#tree-option .el-tree-node')
      allNode.forEach(element => element.classList.remove('is-current'))
    },
    // 懒加载树的方法
    loadNode (node, resolve) {
      if (node.level === 0) {
        this.$emit('loadStart', node, resolve)
      } else {
        this.$emit('loadOther', node, resolve)
      }
    },
    // 自定义搜索方法
    filterMethod (searchStr) {
      this.$emit('search', searchStr)
    }
  },

  watch: {
    value () {
      this.valueId = this.initialId
      this.initHandle()
    }
  }
}
</script>

<style scoped>
.el-scrollbar .el-scrollbar__view .el-select-dropdown__item {
  height: auto;
  max-height: 274px;
  padding: 0;
  overflow: hidden;
  overflow-y: auto;
}
.el-select-dropdown__item.selected {
  font-weight: normal;
}
ul li >>> .el-tree .el-tree-node__content {
  height: auto;
  padding: 0 20px;
}
.el-tree-node__label {
  font-weight: normal;
}
.el-tree >>> .is-current .el-tree-node__label {
  color: #409eff;
  font-weight: 700;
}
.el-tree >>> .is-current .el-tree-node__children .el-tree-node__label {
  color: #606266;
  font-weight: normal;
}
</style>
